A system consisting of a C-arm X-ray device and an electromagnetic position detection system, which position detection system may be additionally configured as a mapping system, is used for example for punctures, general catheter applications or catheter applications in the heart of a patient, the puncture needle or the catheter being navigated and/or guided in the patient on the basis of images of the patient obtained by the C-arm X-ray device and on the basis of position data of the puncture needle or of the catheter obtained by the electromagnetic position detection system and mapping system, by, for example, an image of the puncture needle or of the catheter being superimposed on the images obtained by the C-arm X-ray device. The electromagnetic position detection system and mapping system and the C-arm-X-ray device and/or the electromagnetic position detection system and mapping system and the images obtained by the C-arm-X-ray device are, to this end, generally registered with one another so that an image of the puncture needle or of the catheter may be superimposed on the X-ray images.
When treating cardiac arrhythmia of a patient by so-called ablation, an ablation catheter is inserted via veins or arteries into one of the heart chambers of the patient, for example by means of X-ray images obtained by the C-arm-X-ray device, and the tissue causing the cardiac arrhythmia is removed by high frequency current. A prerequisite for successfully performing a catheter ablation is, on the one hand, the accurate localization of the cause of the cardiac arrhythmia in the heart chamber and, on the other hand, the targeted removal of the tissue causing the cardiac arrhythmia. The tissue is located in an electrophysiological examination, in which electric potential is detected in a localized manner by a mapping catheter inserted into the heart chamber. From this electrophysiological examination, so-called electroanatomical mapping, 3D mapping data of the heart chamber is obtained, for example, which may be visualized on a monitor. The mapping function and the ablation function are, moreover, frequently combined in one catheter so that the mapping catheter is also at the same time an ablation catheter.
A known electroanatomical 3D mapping method, as may be carried out for example by the CARTO system of Biosense Webster Inc., USA, is based on an electromagnetic principle. By means of transmitters arranged beneath a patient positioning device, generally three different electromagnetic fields of low intensity are created. By means of electromagnetic sensors integrated in the catheter tip of the mapping catheter, it is possible to measure the voltage variations within the electromagnetic fields induced by the catheter movements, and by means of mathematical algorithms it is possible to calculate the position of the mapping catheter at any time. By specifically scanning the contour of a heart chamber by the mapping catheter while simultaneously detecting the electrical signals of the sensors, the mapping data is thus obtained and/or an electroanatomical three-dimensional map is produced.
The ablation catheter may, therefore, not only be guided by means of the above-mentioned X-ray images, but also using the electroanatomical mapping data. The X-ray images specifically do not show the anatomy of the patient, in particular the anatomy of the heart of the patient, in detail. A 3D view of anatomical details of the heart could increase the accuracy when carrying out the ablation as regards the morphology of the heart tissue, accelerate the implementation of the ablation and lead to a reduction of the X-ray radiation dose applied to a patient during an ablation.
In complex cases in particular, electrophysiologists welcome being able to carry out the ablation using a combination of electrophysiological and morphological criteria. For the electrophysiologists, therefore, it would be helpful to have available a combined visualization of 3D image data obtained by an imaging device and electroanatomical 3D mapping data.
The reconstruction of a volume data set of the heart of a patient using X-ray projections recorded by a C-arm X-ray device is generally EKG-triggered. Thus from DE 10 2005 016 472 A1, an operating method for an X-ray unit is known in which an X-ray arrangement is repeatedly pivoted between two end positions about a pivot axis. The X-ray arrangement is thus controlled so that, respectively in a plurality of angular positions at detection times, X-ray projections of a mobile object to be examined, which is arranged in the region of the pivot axis, are detected and supplied to a control device which stores the X-ray projections and the corresponding angular positions. The control device also receives an EKG signal relative to the object to be examined, and assigns information corresponding to a phase position of the object to be examined to each stored projection. For the reconstruction of a volume data set, the control device selects those X-ray projections in which the phase position at least approximately corresponds to a reconstruction phase position.
If the patient has cardiac arrhythmia, this form of EKG triggering however, is frequently not ideally suited for generating a volume data set of the heart of the patient which is free of smudges and/or motion artefacts which are produced by the cardiac arrhythmia.